1. Field of the Invention
This invention is related to a projection device, and more particularly, a projection device capable of collecting light densely in a limited space.
2. Description of the Prior Art
To make a projection device suitable for all kinds of applications, users usually have some requirements for the strength of light projected by the projection device. For example, if the environment is rather bright, the image projected by the projection devices with a weaker light source may be easily affected by the environmental lighting, which can cause the loss of image quality. In an environment where the distance between the projection screen and the projection device is rather long, the image projected by the projection device with a weaker light source may be decayed along the distance, which can also cause the loss of image quality. Therefore, how to effectively collect more light into the light splitter system of the projection device in a limited space to improve the strength of light of the image has become a critical issue to be solved.
FIG. 1 shows a projection device 100 according to U.S. Pat. No. 8,690,343. The projection device 100 includes a plurality of first sets of light sources 1101, 1102 and 1103, a plurality of second sets of light sources 1201, 1202, and 1203, a plurality of optical modules 1301, 1302, and 1303, and a light splitter module 140. The optical modules 1301, 1302, and 1303 are disposed along the first axis Y and the second axis Z and parallel to each other. Each of the optical modules 1301, 1302, and 1303 includes a first reflection mirror 132 and a transparent reflection module 134. The first reflection mirror 132 and the transparent reflection module 134 are disposed along the second axis Z and adjacent to each other. The transparent reflection module 134 includes second reflection mirrors 1341 and transparent glasses 1342, where the second reflection mirrors 1341 and the transparent glasses 1342 are disposed with an interleaving manner along the third axis X.
The first set of light sources 1101 is disposed corresponding to the first reflection mirror 132 of the optical module 1301 along the first axis Y, and has the same X coordinate of the third axis X as does the transparent glass 1342 of the transparent reflection module 134. Therefore, the light L1 emitted from the first set of light sources 1101 can be reflected by the first reflection mirror 132 to pass through the transparent glass 1342 of the transparent reflection module 134, and further into the light splitter module 140 after passing through the transparent glass 1342. The second set of light sources 1201 is disposed corresponding to the transparent reflection module 134 of the optical module 1301 along the first axis Y, and has the same X coordinate of the third axis X as does the second reflection mirror 1341 of the transparent reflection module 134. Therefore, the light L2 emitted by the second set of light sources 1201 can be reflected by second reflection mirror 1342 of the transparent reflection module 134 into the light splitter module 140.
The first sets of light sources 1101, 1102, and 1103 are disposed along the second axis Z, the second sets of light sources 1201, 1202, and 1203 are disposed along the second axis Z, and the optical modules 1301, 1302, and 1303 are disposed along the first axis Y and the second axis Z. Therefore the light L1 emitted by the first sets of light sources 1101, 1102, and 1103 can all be directed to the light splitter module 140 by the optical modules 1301, 1302, and 1303 respectively, and the light L2 emitted by the second sets of light sources 1201, 1202, and 1203 can all be directed to the light splitter module 140 by the optical modules 1301, 1302, and 1303 respectively.
Although the projection device proposed by U.S. Pat. No. 8,690,343 can collect more light into the light splitter module 140 in a limited space, when disposing the first sets of light sources and the second sets of light sources, the position along the third axis X must be considered, that is, the first sets of light sources and the second sets of light sources must be disposed corresponding to the second reflection mirror and the transparent glass of the transparent reflection module respectively, which can increase the complexity for implementation. Especially in such a limited space within the projection device, this kind of detail arrangement can be even more difficult, which may cause difficulty in improving the yield rate.